With the equivalent of a full season as Red Sox closer under his belt, hitters know he plans to retire them with fastballs and splitters. And they know he’s going to throw strikes.

Lots of strikes.

It came as no surprise then that the Cubs — a team that hasn’t seen Uehara in a Red Sox uniform before Tuesday — were aggressive in their approach in the top of the ninth inning at Fenway Park.

In a game tied at one, Anthony Rizzo jumped on the first pitch he saw — a splitter — and singled. Cleanup man Starline Castro saw five pitches before doubling on a fastball that caught a chunk of the plate. Luis Valbuena knocked in the game-winning run seven pitches later on a splitter he lifted to right field for a sacrifice fly.

After the loss, Uehara told reporters that he’s feeling “a little bit of fatigue.” He didn’t hint any any soreness, however, and didn’t blame his night on overuse.

“I probably need to get younger,” he explained through team interpreter C.J. Matsumoto.

Kidding aside, Uehara did admit that the command of his splitter isn’t where he would like it. Lately, that has translated into a handful of runs allowed.

Since a 2-1 win in Minnesota on June 18, Uehara has thrown seven innings, allowing four runs and seven hits.

Red Sox manager John Farrell said that when Uehara has run into trouble it has been against teams that were aggressive, as the Cubs were Tuesday.

“A number of early swings,” Farrell said. “When he’s giving up some base hits, it’s been on first or second pitch where he’s trying to get a strike. It’s not the true put-away split.

“That was the case with Rizzo tonight. I thought Castro laid off some pretty good splits to get deep in that count and then gets one up in the strike zone for the double. It’s been more in the early counts where we’ve seen some of the damage take place.”

It’s been unusual for Uehara to run into any trouble so his posting a 5.14 ERA in eight outings has been a strange sight. But his teammates aren’t concerned.

Clay Buchholz — Tuesday’s starter for the Sox, who gave up one run in 6.1 innings — said that everyone on the team still takes a deep breath every time they see Uehara make his way in from the bullpen.

“Can’t go out and not give up a run every time out,” Buchholz said. “It’s impossible. As far as I’m concerned, he’s the best closer-slash-reliever in the game . . . Things happen. This game’s hard. Regardless of if you throw 120 mph somebody’s gonna get a hit off it and score a run.”

Catcher AJ Pierzynski had his closer’s back as well.

“Everyone knows Koji throws fastball and split pretty much, so he makes a good pitch he gets guys out,” he said. “It’s not like he’s been getting crushed all over the yard. He got a bunch of saves on the road trip. Threw the ball fine, like I said. Rizzo hit a good pitch. Castro hit a pretty good pitch, and then Valbuena had a good at-bat and hit one just far enough. I mean, I don’t know what you guys want.”

Rightly or wrongly, these are the standards Uehara has set for himself. The good news for the Red Sox is that he doesn’t seem too far out of whack. He’s just a couple of weeks removed from polishing off a streak of 21 consecutive scoreless innings.

And his plan for getting back into a groove, like his approach on the mound, was remarkably simple as he explained it.

“Just get some sleep . . . eat well,” he said. “I think it comes down to the basic stuff.”